JP2000276723A - Detector for head clogging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable clogging detector which is inexpensive and capable of readily shifting to the next information recording. SOLUTION: A rotary cylinder 2 is provided with a first and a second head 3a, 3b each having a different azimuth angle, so that a signal is recorded simultaneously in an adjacent track in a magnetic tape 1. At the time of recording of information, the information and a pilot signal are recorded and, upon completion of the recording of the information, the transfer of the magnetic tape 1 is quickly stopped. Then, the track recorded by the second head 3b is obliquely scanned by the first head 3a. In this case, if the pilot signal recorded by the second head 3b is detected, a clogging detecting circuit 10 judges it as no clogging. If the level of the pilot signal is at a threshold value or below, it is judged as either the first or the second head is clogged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for performing helical scanning of a magnetic tape by a rotary cylinder and recording / reproducing information via a magnetic head. The present invention relates to a detection device.

[0002]

2. Description of the Related Art As a conventional head clogging detecting device,
For example, JP-A-59-104707 discloses a configuration example and operation thereof. In this apparatus, a magnetic head for simultaneous reproduction (hereinafter, referred to as a simultaneous reproduction head) is provided on a rotating cylinder at a position different from a magnetic head exclusively for recording (hereinafter, referred to as a recording-only head), and the same track is read from a track immediately after recording. The clogging of the head during recording is detected by reproducing the signal with the azimuth head and determining the level of the reproduced signal.

In a magnetic recording / reproducing apparatus having no simultaneous reproducing head, the magnetic tape is rewound once after recording, and thereafter, the already recorded track is reproduced to determine whether there is any recording omission due to clogging. Had been detected.

[0004]

However, in the above-described configuration and method, a simultaneous reproducing head is required to detect recording omission due to clogging of the head. Along with this, a rotary transformer, a rotary cylinder with little crosstalk, and the like are required, and the configuration of the cylinder unit is complicated, and the price is extremely high. Further, in a magnetic recording / reproducing apparatus having no simultaneous reproducing head, it is necessary to rewind and reproduce the magnetic tape once, and there is a drawback that it is not possible to immediately proceed to the next recording operation.

[0005] For this reason, up to now, it has not been possible to inexpensively construct a practical device capable of constantly monitoring recording leakage due to head clogging. In particular, there has been a demand for an inexpensive method of performing intermittent recording and constantly monitoring whether there is any missing recording in a monitoring VTR (time-lapse VTR) requiring reliability.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has as its object to provide a highly reliable head clogging detection device which can always detect a recording leak even during intermittent recording. And

[0007]

According to a first aspect of the present invention, there is provided a rotary cylinder for rotating a tape-shaped magnetic recording medium by obliquely winding the magnetic recording medium on the rotary cylinder, and rotating the tape-shaped magnetic recording medium approximately one above the rotary cylinder.
A first head and a second head having different azimuth angles, which are mounted at different track pitches, record signals almost simultaneously on odd tracks and even tracks of the recording medium, and simultaneously reproduce the recorded signals; After the recording is completed, the running of the recording medium is temporarily stopped, and based on the output level of the signal of the even-numbered track reproduced by the first head, whether or not the first head or the second head is clogged is determined. And a clogging detection circuit for detecting the clogging.

According to a second aspect of the present invention, in the head clogging detecting device of the first aspect, the clogging detecting circuit is configured such that a low-frequency pilot signal is superimposed on an information signal and recorded by the second head. Detecting whether the first head or the second head is clogged based on the level of the pilot signal reproduced by the first head.

According to a third aspect of the present invention, there is provided a rotating cylinder which winds and rotates a tape-shaped magnetic recording medium obliquely,
It is mounted on the rotating cylinder close to and shifted by about one track pitch, and signals are simultaneously sent to odd and even tracks of the recording medium once every n rotations of the rotating cylinder with respect to tracks of the recording medium. A first head and a second head having different azimuth angles for recording and simultaneously reproducing a recorded signal, and a signal of a track recorded by the second head are recorded by the first head except when recording. A clogging detection circuit that reproduces data during a period in which the recording head is in contact with the recording medium and detects whether the first head or the second head is clogged based on a reproduced signal level. It is assumed that.

According to a fourth aspect of the present invention, in the head clogging detecting device of the third aspect, the clogging detecting circuit is configured such that a low-frequency pilot signal is superimposed on an information signal and recorded by the second head. Detecting whether the first head or the second head is clogged based on the level of the pilot signal reproduced by the first head.

According to a fifth aspect of the present invention, there is provided a rotating cylinder which winds and rotates a tape-shaped magnetic recording medium obliquely,
A first head and a second head having different azimuth angles, which are mounted on the rotating cylinder and alternately record signals on tracks of the recording medium, and reproduce the recorded signals, and the second head. A clogging detection circuit for detecting the presence or absence of clogging of the first head or the second head based on an output level of a recorded track signal reproduced by the first head. It is characterized by the following.

According to a sixth aspect of the present invention, in the head clogging detecting device of the fifth aspect, the clogging detecting circuit is configured such that a low-frequency pilot signal is superimposed on an information signal and recorded by the second head. Detecting whether the first head or the second head is clogged based on the level of the pilot signal reproduced by the first head.

According to a seventh aspect of the present invention, there is provided a rotary cylinder for rotating a tape-shaped magnetic recording medium by winding it obliquely,
A first head mounted on the rotating cylinder and having a different azimuth angle for alternately recording a signal once every n rotations of the rotating cylinder on a track of the recording medium, and reproducing the recorded signal; A second head and a signal of a track recorded by the second head are reproduced during a period in which the first head is in contact with the recording medium other than during recording, and the second signal is reproduced based on a reproduced signal level. A clogging detection circuit for detecting whether or not the first head or the second head is clogged.

According to an eighth aspect of the present invention, in the head clogging detecting device according to the seventh aspect, the clogging detecting circuit is configured such that a low frequency pilot signal is superimposed on an information signal and recorded by the second head. Detecting whether the first head or the second head is clogged based on the level of the pilot signal reproduced by the first head.

According to such a configuration, since the track recorded by the second head is reproduced by the first head and clogging of both heads is detected at a time, an extra head is added. Thus, an inexpensive head clogging detection device can be provided.

Further, since the clogging is detected during the stop of traveling after the end of the recording or during a period of one blank hit recording in the rotation of the cylinder n, there is no need to rewind the tape, and the recording is immediately shifted to the next recording. can do. Thus, it is possible to provide a highly reliable head clogging detection device capable of always detecting a recording leak for a monitoring VTR that performs intermittent recording.

[0017]

(Embodiment 1) A head clogging detection apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. This head clogging detection device is applied to a monitoring VTR that performs an intermittent recording operation. FIG. 1 is a schematic configuration diagram of a head clogging detection device according to the present embodiment. FIG. 2 is an operation explanatory diagram showing waveforms of respective parts in FIG. 1, and FIG. 3 is an explanatory diagram showing a relationship between a scanning locus of a head on a magnetic tape and a recorded track pattern.

In FIG. 1, a magnetic tape 1 is helically wound around a rotary cylinder 2 and transported in the direction of the arrow. In the recording or normal reproduction mode, the rotary cylinder 2 rotates at the specified speed ω, and the magnetic tape 1 is transported at the normal speed V0. The rotary cylinder 2 includes a first head 3a and a second head 3a.
Of heads 3b are mounted close to each other. The first head 3a and the second head 3b have different azimuths, and the mounting height with respect to the rotary cylinder 2 is different by one track pitch.

At the time of normal recording, the magnetic tape 1 is transported at the normal speed V0, and input signals such as video signals are input to the recording signal processing circuits 5a and 5b. Recording signal processing circuit 5
The outputs of a and 5b are switches 8a and 8b operating in conjunction with each other.
Through the first head 3a and the second head 3b. Recording signal processing circuit 5a,
5b performs digitization, compression, and encoding of the input video signal, and performs addition of additional information and audio signals, addition of an error correction signal, and the like. And the recording signal processing circuits 5a, 5b
Modulates an encoded digital signal into a signal for a recording medium and supplies the signal to a first head 3a and a second head 3b, respectively. Thus, a signal is recorded on each track of the magnetic tape 1.

If the switches 8a and 8b are switched to the recording signal processing circuit side, the recording signal corresponding to the information to be recorded is input to the first head 3a as it is. Further, the pilot generation circuit 7 generates a pilot signal having a low frequency with low azimuth loss. This pilot signal is superimposed on the information signal output from the recording signal processing circuit 5b via the addition circuit 6. Thus, the recording signal on which the pilot signal is superimposed is input to the second head 3b. In the configuration shown in FIG. 1, during the rotation of the rotary cylinder 1, the first 180-degree period (t 1 to t in FIG.
, T3 to t4, t5 to t6,...), None of the heads is in contact with the magnetic tape 2. Such a period is the first
The head 3a and the second head 3b are off when viewed from the recording signal processing circuit 5.

The second 180-degree period (to t1, t2 to t)
, T4 to t5,...) Are connected to the first head 3a and the second head 3b to the recording signal processing circuit side. The first head 3a and the second head 3b scan the magnetic tape 1 with a shift of one track pitch to the rear side as compared with the case where the rotation phase of the rotary cylinder 1 is 0 to 180 degrees. Record the signals simultaneously. That is, FIG.
As shown in (b), the rotation phase 180 of the rotary cylinder 2
At 360 degrees, the first head 3a records a signal on an odd track and the second head 3b records a signal on an even track in each of the periods A, B, and C in the figure.

The magnetic tape 1 is continuously transported by the capstan motor 4 at a rate of one track, that is, at a normal linear velocity V0, by a half rotation of the rotary cylinder 2. When the periods A, B, and C end, the capstan motor 4 is immediately decelerated from the time t5 to the next recording timing (time t5).
The transfer of the magnetic tape 1 is stopped until s). At this time, from time t5, the switches 8a and 8b
Switch to a, 9b side. Assuming that the magnetic tape 1 stops at a time t6, that is, a half cycle time of the rotary cylinder 2 from the time t5, as shown in FIG.
During the periods D, E, and F (the period from time t6 to ts in FIG. 2),
The scanning is performed on the even-numbered track recorded by the second head 3b immediately before. At this time, in the even-numbered track recorded by the second head 3b, a pilot signal is recorded in advance in a low frequency band where azimuth loss is small so as to be superimposed on an original information signal. Therefore, during the period from the time t6 when the transfer of the magnetic tape 1 is stopped to the time ts when the next recording is started, the reproduced waveforms of the first head 3a and the second head 3b obtained by rotating the rotary cylinder 2 are as follows. 2 (c) and 2 (d).

In the waveform shown in FIG. 2C, the signal Sb having a hexagonal envelope is a reproduced waveform of a signal recorded by the second head 3b. A signal Sa having a triangular envelope shape is a reproduced waveform of a signal recorded by the first head 3a. Such a reproduced waveform is obtained because the first head 3a scans the track 3b-C obliquely during the D, E, and F scanning periods as shown in FIG. As shown in FIG. 2D, the signal Sc having the triangular envelope shape is such that the second head 3b scans the track 3b-C diagonally, and the second head 3b performs the previous recording at the track end. This is the read signal.

Next, the clogging detection circuit 10 shown in FIG. 1 detects the reproduced waveform of the first head 3a and generates a detected waveform as shown in FIG. 2 (e). By comparing the amplitude of this detection waveform with the reference threshold, a clogging detection output shown in FIG. In this case, without rewinding the magnetic tape 1 and using a normal recording and reproducing head,
Head clogging can be detected.

As described above, when the first head 3a reproduces the pilot signal of the track recorded by the second head 3b, clogging of both heads can be detected at once. Thus, the head clogging detection device can be realized at low cost using the existing cylinder unit without adding an extra head. Furthermore, after recording two tracks simultaneously using a pair head mounted adjacently on the rotary cylinder 2, within a period in which no recording is performed,
Since the transfer of the magnetic tape 1 is stopped, the first head can sufficiently reproduce the track written by the second head as described above. Further, during a period in which both heads are not in contact with the magnetic tape 1, the magnetic tape is decelerated or accelerated to a desired speed or a stopped state,
Information can be recorded without gaps without bending the track.

As described above, by using the rotating cylinder having the paired head structure in which the head is moved to one side, the recording data can be checked while detecting clogging every recording without rewinding the magnetic tape. . Further, as in the period G in FIG. 2, a highly reliable intermittent recording operation that can immediately shift to the next recording can be realized.

In the above configuration, the first head 3a and the second head 3b are moved close to the rotary cylinder 2 by approximately one.
The magnetic tape 1 was mounted so as to be shifted in track pitch, and signals were recorded almost simultaneously on odd tracks and even tracks of the magnetic tape 1. On the other hand, the first head 3a and the second head 3b having different azimuth angles are attached to the rotary cylinder 2 at positions opposite to each other by 180 degrees so that signals are alternately recorded on tracks of the magnetic tape 1. Is also good.

(Embodiment 2) Next, a head clogging detection apparatus according to Embodiment 2 of the present invention will be described with reference to the drawings. The schematic configuration of the head clogging detection device according to the present embodiment is the same as that of FIG. FIG. 4 is a diagram illustrating the operation of the clogging detection device according to the present embodiment. As in the case of the first embodiment, the first and second heads 3a and 3b have different azimuths, and are mounted adjacent to the rotary cylinder 2 with their heights shifted by one track pitch. Here, instead of intermittently feeding the magnetic tape 1, when the rotating cylinder 2 rotates n times, one of the rotations is used for the recording operation. That is, the present invention is directed to a magnetic recording / reproducing apparatus which performs recording at a frame rate of 1 / n of the normal recording. In this case, the magnetic tape 1 is rotated by controlling the rotation of the capstan motor 4 so that V1 = (1/1).
n) Transfer at the speed of V0.

In the following description, it is assumed that n = 2, the rotary cylinder 2 is rotated at a normal angular velocity ω, and when the rotary cylinder 2 makes two rotations, the first and second heads 3a, 3a,
It is assumed that information is simultaneously recorded on two tracks using 3b. As shown in FIG. 4A, the transfer speed V1 of the magnetic tape 1 is set to (1/2) V0, and as shown in FIGS. 4B to 4D, the first and second heads 3a, 3b Is a rotation period during which recording is not performed, and the first and second heads 3
During the period in which the first and second heads 3a and 3b are in contact with the magnetic tape 1, the switches 8a and 8b are switched to the reproduction signal processing circuit side. To play. The second head 3b also obtains a low-level signal from this track.

Also in this example, a low-frequency pilot component with a small azimuth loss is superimposed on the recording signal of the second head 3b. Therefore, as shown in FIG. 4C, the component can be detected with a sufficient S / N from the reproduced waveform of the first head 3a. That is, also in this example, the clogging detection circuit 10 can detect clogging of both heads at a time by reproducing a track recorded by one of the heads having different azimuths immediately thereafter with the other head. Therefore, a head clogging detection device can be provided at low cost. In addition, in frame-drop recording, clogging can be detected every time recording is performed without rewinding the magnetic tape 1 and recording can be checked, so that a highly reliable monitoring VTR can be provided.

In this embodiment, the first head 3a and the second head 3b are mounted close to each other on the rotary cylinder 2 so as to be shifted by approximately one track pitch, and signals are placed on odd and even tracks of the magnetic tape 1. At almost the same time. On the other hand, the first head 3a and the second head 3b having different azimuth angles are
May be attached at positions 180 degrees opposite to each other to record signals alternately on tracks of the magnetic tape 1.

Further, in the above configuration, the pilot component is superimposed on the low frequency band where the azimuth loss is small. However, the present invention is not limited to these embodiments, and the frequency domain may be divided and divided. Alternatively, the presence or absence of an information signal may be detected without superimposing a pilot signal. The information is digitally modulated and recorded on the magnetic tape 1. If the head is not clogged, a signal corresponding to the recording wavelength (magnetization reversal period) should be obtained regardless of the data content. Thus, various modifications are possible within the scope of the present invention.
Further, some of the present inventions may be combined at the same time.

[0033]

As described above, according to the first, second, fifth, and sixth aspects of the present invention, the tracks recorded by the second head are reproduced by the first head so that both heads are clogged once. , Without adding an extra head,
An inexpensive head clogging detection device can be provided.

According to the third, fourth, seventh and eighth aspects of the present invention, clogging is detected during the stoppage of travel after the end of recording or during the period of one blank hit recording every n rotations of the rotary cylinder.
There is no need to rewind the magnetic tape, and it is possible to immediately proceed to the next recording. Thus, it is possible to provide a highly reliable head clogging detection device capable of always detecting a recording omission, particularly for a monitoring VTR that performs intermittent recording.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a head clogging detection device according to Embodiments 1 and 2 of the present invention.

FIG. 2 is an operation explanatory diagram of the head clogging detection device according to the first embodiment.

FIG. 3 is a tape pattern diagram showing a relationship between a scanning locus of a head on a magnetic tape and a recorded track.

FIG. 4 is an operation explanatory diagram of a head clogging detection device according to a second embodiment. You.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic tape 2 Rotating cylinder 3a 1st head 3b 2nd head 4 Capstan motor 6 Addition circuit 5a, 5b Recording signal processing circuit 7 Pilot generation circuit 8a, 8b Switch 9a, 9b Reproduction signal processing circuit 10 Clogging detection circuit

Claims (8)

[Claims] 1. A rotary cylinder for rotating a tape-shaped magnetic recording medium by obliquely winding the same, and being mounted on the rotary cylinder in proximity to each other with a pitch of approximately one track, and a signal is supplied to an odd track and an even track of the recording medium. And a first head and a second head having different azimuth angles for simultaneously reproducing the recorded signals, and temporarily stopping the running of the recording medium after the recording of the information, and A clogging detection circuit for detecting the presence or absence of clogging of the first head or the second head based on an output level reproduced by the first head. Clog detection device. 2. The clogging detection circuit, when a low-frequency pilot signal is superimposed on an information signal and recorded by the second head, the level of the pilot signal reproduced by the first head is reduced. The head clogging detection device according to claim 1, wherein the presence or absence of clogging of the first head or the second head is detected based on the detection. 3. A rotary cylinder for rotating a tape-shaped magnetic recording medium by obliquely winding the same, and being mounted on the rotary cylinder in proximity to each other and shifted by approximately one track pitch, wherein the rotary cylinder is mounted on a track of the recording medium. A first head and a second head having different azimuth angles for simultaneously recording signals on odd-numbered tracks and even-numbered tracks of the recording medium and reproducing the recorded signals simultaneously once every n rotations of the recording medium; A signal of a track recorded by the second head is reproduced during a period in which the first head is in contact with the recording medium except at the time of recording, and the first head or the second signal is reproduced based on a reproduced signal level. A clogging detection circuit for detecting whether or not the head is clogged. 4. The clogging detection circuit, when a low-frequency pilot signal is superimposed on an information signal and recorded by the second head, the level of the pilot signal reproduced by the first head is reduced. 4. The head clogging detection device according to claim 3, wherein the presence or absence of clogging of the first head or the second head is detected based on the detection. 5. A rotary cylinder that rotates by rotating a tape-shaped magnetic recording medium obliquely, and is mounted on the rotary cylinder, and alternately records signals on tracks of the recording medium and reproduces the recorded signals. A first head and a second head having different azimuth angles, and a signal of a track recorded by the second head,
Clogging detection circuit for detecting whether the first head or the second head is clogged based on an output level reproduced by the first head. Detection device. 6. The clogging detection circuit, when a low-frequency pilot signal is superimposed on an information signal and recorded by the second head, the level of the pilot signal reproduced by the first head is reduced. The head clogging detection device according to claim 5, wherein the presence or absence of clogging of the first head or the second head is detected based on the detection. 7. A rotating cylinder that rotates by rotating a tape-shaped magnetic recording medium obliquely, and is mounted on the rotating cylinder, and alternately once every n rotations of the rotating cylinder with respect to a track of the recording medium. A first head and a second head having different azimuth angles for recording a signal and reproducing the recorded signal; and a first head for recording a signal of a track recorded by the second head except for recording. Comprises a clogging detection circuit that reproduces during a period in which the recording head is in contact with the recording medium, and detects whether the first head or the second head is clogged based on a reproduced signal level. Head clogging detection device. 8. The clogging detection circuit, when a low-frequency pilot signal is superimposed on an information signal and recorded by the second head, the level of the pilot signal reproduced by the first head is reduced. 8. The head clogging detection device according to claim 7, wherein the presence or absence of clogging of the first head or the second head is detected based on the detection.